<template>
  <div :style="{ height: height + 'px', zIndex: zIndex }">
    <div
      :class="className"
      :style="{
        top: isSticky ? stickyTop + 'px' : '',
        zIndex: zIndex,
        position: position,
        width: width,
        height: height + 'px',
      }"
    >
      <slot></slot>
    </div>
  </div>
</template>

<script>
  export default {
    name: "VabSticky",
    props: {
      stickyTop: {
        type: Number,
        default: 0,
      },
      zIndex: {
        type: Number,
        default: 1,
      },
      className: {
        type: String,
        default: "",
      },
    },
    data() {
      return {
        active: false,
        position: "",
        width: undefined,
        height: undefined,
        isSticky: false,
      };
    },
    mounted() {
      this.height = this.$el.getBoundingClientRect().height;
      window.addEventListener("scroll", this.handleScroll);
      window.addEventListener("resize", this.handleResize);
    },
    activated() {
      this.handleScroll();
    },
    destroyed() {
      window.removeEventListener("scroll", this.handleScroll);
      window.removeEventListener("resize", this.handleResize);
    },
    methods: {
      sticky() {
        if (this.active) {
          return;
        }
        this.position = "fixed";
        this.active = true;
        this.width = this.width + "px";
        this.isSticky = true;
      },
      handleReset() {
        if (!this.active) {
          return;
        }
        this.reset();
      },
      reset() {
        this.position = "";
        this.width = "auto";
        this.active = false;
        this.isSticky = false;
      },
      handleScroll() {
        const width = this.$el.getBoundingClientRect().width;
        this.width = width || "auto";
        const offsetTop = this.$el.getBoundingClientRect().top;
        if (offsetTop < this.stickyTop) {
          this.sticky();
          return;
        }
        this.handleReset();
      },
      handleResize() {
        if (this.isSticky) {
          this.width = this.$el.getBoundingClientRect().width + "px";
        }
      },
    },
  };
</script>
